Template to use TypeScript with k6

This repository provides a scaffolding project to start using TypeScript in your k6 scripts.

Rationale

While JavaScript is great for a myriad of reasons, one area where it fall short is type safety and developer ergonomics. It's perfectly possible to write JavaScript code that will look OK and behave OK until a certain condition forces the executor into a faulty branch.

While it, of course, still is possible to shoot yourself in the foot with TypeScript as well, it's significantly harder. Without adding much overhead, TypeScript will:

• Improve the ability to safely refactor your code.
• Improve readability and maintainability.
• Allow you to drop a lot of the defensive code previously needed to make sure consumers are calling functions properly.

Installation

Creating a project from the template-typescript template

To generate a TypeScript project that includes the dependencies and initial configuration, navigate to the template-typescript page and click Use this template.

Install dependencies

Clone the generated repository on your local machine, move to the project root folder and install the dependencies defined in package.json

npm install

Running the test

To run a test written in TypeScript, we first have to transpile the TypeScript code into JavaScript running the bundler:

npm run bundle

This command creates the final test files to the ./dist folder.

Once that is done, we can run our script the same way we usually do, for instance:

k6 run dist/get-200-status-test.js

Running the test inside Docker

docker run --rm -i -v $(pwd)/dist:/dist -w /dist grafana/k6 run get-200-status-test.js

Running with Docker

You can run the performance tests using Docker Compose, which handles all the dependencies and building automatically:

docker-compose up --build

This will:

1. Build the project using Node.js (including npm install and bundling)
2. Run the k6 performance tests

For faster builds, if you have already run npm install locally, the build process will reuse your local node_modules directory.

Transpiling and Bundling

By default, k6 does not support TypeScript, but it supports ES modules and ES5.1 code with CommonJS modules. To use TypeScript, we have to set up a bundler that converts TypeScript to any of these formats.

This project uses Babel and Webpack to bundle the different files into CommonJS modules, using its webpack.config.js configuration.

The bundled tests will be transpiled to ES5.1 code with CommonJS modules, this allows running the tests with --compatibility-mode=base for better performance:

k6 run --compatibility-mode=base dist/get-200-status-test.js

Writing own tests

House rules for writing tests:

• The test code is located in src folder
• The entry points for the tests need to have "test" word in the name to distinguish them from auxiliary files. You can change the entry here.
• If static files are required then add them to ./assets folder. Its content gets copied to the destination folder (dist) along with compiled scripts.

Learn more

• k6 Docs: working with modules
• JavaScript Compatibility Mode
• grafana/k6-rollup-example